The present invention relates to an improved leveling system for motor vehicles particularly used by industrial vehicles with a dump body. Vehicles equipped with dump bodies have a frame connected to the wheels by suspension and supported by an auxiliary frame which is hinged to the dump body pivoted by a shaft positioned at the rear end of the vehicle.
To dump loose material such as soil, sand etc., the dump body is raised until it reaches an angle in relation to the frame which will enable the dump body to be emptied.
This operation can be carried out when the vehicle is stationary but in most cases the vehicle is simultaneously driven forward to facilitate the tipping out of the load.
When the vehicle, which may be a truck, a semi-trailer or a trailer is on safe, solid ground, for example a flat, tarred surface, dumping operations are usually carried out safely and without problems. When the ground the vehicle is standing on is not level, on the other hand, raising the body to dump the material being carried is difficult and may be very dangerous.
In fact, if the wheels of the vehicle, particularly the back wheels, do not have a sufficiently solid support, the vehicle tilts (and rolls about its longitudinal axis) placing more weight on one side of it than on the other.
Such situations are relatively frequent and make it difficult to manage the beginning of dumping operations. The stability of the ground on which the vehicle has to work is not always easy to judge since the vehicles concerned are used on building sites and landfills, where the surface is covered by a layer of loose material compacted to varying degrees.
For this reason, even if the wheels on the rear axle (or axles) may be perfectly level when the vehicle starts dumping, the increased weight bearing on the rear axle may cause the vehicle to gradually tilt to one side as the dumping operation proceeds. Although the tilt angle may be just a few degrees at the base, it is much greater at the top when the dump body is raised and leads to irregular dumping. If the load to be dumped is wet soil or similar material, the dumping operation is even more critical; such materials, once the vehicle is tilted sideways, tend to come loose mainly on the side opposite the tilted side, thus making the load on the vehicle even more imbalanced by increasing the mass weighing down on one side of the axle.
As a result, the vehicle becomes much more unstable during dumping operations, creating an obvious hazard for the operator (driver) and the risk of damaging the vehicle itself.
Moreover, should the vehicle roll over completely, not only is the driver's life at risk but also the lives of any persons who may be working near the vehicle. Since the dump command is normally given from inside the cab, the drivers of the vehicles often have to work under very awkward conditions. In practice, a driver must dump the load, if necessary by inching the vehicle forward and stopping it alternately, without being able to check the real state of the load or to fully control the dumping operation and while being constantly on guard against the risk of rolling over.
At present, the stability of a vehicle during dumping operations, is guaranteed by the strength of the connection between the frame and auxiliary frame, which subjects the vehicle structure to considerable torsional strain.
For this reason, the frame and the auxiliary frame must be appropriately constructed but even a strong structure may be insufficient to prevent rolling over or damage in the event of abrupt yielding or subsidence of the ground under the vehicle wheels.
A solution to these problems has been provided by the same Applicant with the invention disclosed in the patent application IT-BO95A 000106. The previous patent application relates to a leveling system which enables the hinged shaft between the dump body and the auxiliary frame to remain horizontal, thus enabling the material in the truck to be dumped safely and easily.
The leveling system disclosed in the above mentioned application basically includes means for detecting the inclination of the hinged shaft between the dump body and the auxiliary frame to the horizontal and means for adjusting the inclination consisting of a pivoted lever or bracket which is acted on by at least two variable extension elements located on opposite sides of the pivot and designed to adjust the inclination in accordance with the readings of the detecting means.